I can’t install Comodo Firewall Pro
If you had a different firewall installed, prior to installing CFP, it’s possible that some remnants of the old firewall still remain on the PC. This may cause the installation of CFP to fail.
You must ensure all traces of a previous firewall are removed before installing CFP.
If you’re having difficulties removing your existing firewall, you should check the vendors web site for extended uninstall instructions. Here are a few links for some firewalls:
Outpost: Extended Application or Firewall Uninstall/Install Instructions
Zone Alarm: http://www.nohold.net/noHoldCust25/Prod_1/Articles55646/CompleteUninstallNonNT.html
If you are re-installing CFP and the installation fails with a message to the effect, that an Older version is still installed. See this link.